Change creation of relative relocations on COFF

[• rafael]

Summary

For whatever reason, when processing

.globl  foo

foo:

.data

bar:

.long   foo-bar

llvm-mc creates a relocation with the section:

0x0 IMAGE_REL_I386_REL32 .text

This is different than when the relocation is relative from the beginning. For example, a file with

call foo

produces

0x0 IMAGE_REL_I386_REL32 foo

I would like to refactor the logic for converting "foo - ." into a relative relocation so that it is shared with ELF. This is the first step and just changes the coff implementation to match what ELF (and COFF in the case of calls) does.

[ruiu]

LGTM

[• espindola]

306063

[• espindola]

306063

lib/MC/WinCOFFObjectWriter.cpp

void WinCOFFObjectWriter::recordRelocation(
   }
 
   COFFRelocation Reloc;
 
   Reloc.Data.SymbolTableIndex = 0;
   Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
 
   // Turn relocations for temporary symbols into section relocations.
-  if (A.isTemporary() || SymB) {
+  if (A.isTemporary()) {
     MCSection *TargetSection = &A.getSection();
     assert(
         SectionMap.find(TargetSection) != SectionMap.end() &&
         "Section must already have been defined in executePostLayoutBinding!");
     Reloc.Symb = SectionMap[TargetSection]->Symbol;
     FixedValue += Layout.getSymbolOffset(A);
   } else {
     assert(

test/MC/COFF/cross-section-relative.s

 // READOBJ:    LineNumberCount: 0
 // READOBJ:    Characteristics [ (0xC0500040)
 // READOBJ:      IMAGE_SCN_ALIGN_16BYTES (0x500000)
 // READOBJ:      IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
 // READOBJ:      IMAGE_SCN_MEM_READ (0x40000000)
 // READOBJ:      IMAGE_SCN_MEM_WRITE (0x80000000)
 // READOBJ:    ]
 // READOBJ:    SectionData (
-// READOBJ:      0000: 10000000 00000000 0C000000 00000000  |................|
-// READOBJ:      0010: 08000000 00000000 0C000000 00000000  |................|
+// READOBJ:      0000: 08000000 00000000 04000000 00000000  |................|
+// READOBJ:      0010: 00000000 00000000 04000000 00000000  |................|
 // READOBJ:      0020: 01020000 00000000 00010000 00000000  |................|
-// READOBJ:      0030: 0C000000 00000000                    |........|
+// READOBJ:      0030: 04000000 00000000                    |........|
 // READOBJ:    )
 // READOBJ:  }
 // READOBJ:  ]
 // READOBJ:  Relocations [
 // READOBJ:  Section (5) .fix {
 // READOBJ:    Relocation {
 // READOBJ:      Offset: 0x0
 // READOBJ:      Type: IMAGE_REL_AMD64_REL32 (4)
-// READOBJ:      Symbol: .rdata
+// READOBJ:      Symbol: g3
 // READOBJ:    }
 // READOBJ:    Relocation {
 // READOBJ:      Offset: 0x8
 // READOBJ:      Type: IMAGE_REL_AMD64_REL32 (4)
-// READOBJ:      Symbol: .rdata
+// READOBJ:      Symbol: g3
 // READOBJ:    }
 // READOBJ:    Relocation {
 // READOBJ:      Offset: 0x10
 // READOBJ:      Type: IMAGE_REL_AMD64_REL32 (4)
-// READOBJ:      Symbol: .rdata
+// READOBJ:      Symbol: g3
 // READOBJ:    }
 // READOBJ:    Relocation {
 // READOBJ:      Offset: 0x18
 // READOBJ:      Type: IMAGE_REL_AMD64_REL32 (4)
-// READOBJ:      Symbol: .rdata
+// READOBJ:      Symbol: g3
 // READOBJ:    }
 // READOBJ:    Relocation {
 // READOBJ:      Offset: 0x1C
 // READOBJ:      Type: IMAGE_REL_AMD64_ADDR32NB (3)
 // READOBJ:      Symbol: g3
 // READOBJ:    }
 // READOBJ:    Relocation {
 // READOBJ:      Offset: 0x30
 // READOBJ:      Type: IMAGE_REL_AMD64_REL32 (4)
-// READOBJ:      Symbol: .rdata
+// READOBJ:      Symbol: g3
 // READOBJ:    }

test/MC/COFF/diff.s

_rust_crate:
   .long   0
   .long   _foobar
   .long _foobar-_rust_crate
   .long _foobar-_rust_crate
 
 // CHECK:        Name: .data
 // CHECK:        Relocations [
 // CHECK-NEXT:     0x4 IMAGE_REL_I386_DIR32 _foobar
-// CHECK-NEXT:     0x8 IMAGE_REL_I386_REL32 .text
-// CHECK-NEXT:     0xC IMAGE_REL_I386_REL32 .text
+// CHECK-NEXT:     0x8 IMAGE_REL_I386_REL32 _foobar
+// CHECK-NEXT:     0xC IMAGE_REL_I386_REL32 _foobar
 // CHECK-NEXT:   ]
 // CHECK:        SectionData (
-// CHECK-NEXT:     0000: 00000000 00000000 1C000000 20000000
+// CHECK-NEXT:     0000: 00000000 00000000 0C000000 10000000
 // CHECK-NEXT:   )
 
 // CHECK:        Name: baz
 // CHECK:        Relocations [
 // CHECK-NEXT:   ]
 // CHECK:        SectionData (
 // CHECK-NEXT:     0000: A1300000 00C3C3
 // CHECK-NEXT:   )